Verizon Communications Inc. is buying AOL Inc. in a $4.4 billion deal aimed at advancing the telecom giant's growth ambitions in mobile video and advertising. The all-cash deal values AOL at $50 a share, a 23% premium over the company's three-month volume-weighted average price. AOL shares rose 18% in premarket trading to $50.27. Verizon shares fell 1.6% to $49. The acquisition would give Verizon, which has set its sights on entering the crowded online video marketplace, access to advanced technology AOL has developed for selling ads and delivering high-quality Web video.